The Commentary of City Promotional Films Based on Transitivity Theory: A Case Study of Xi’an and San Francisco

Based on Halliday's theory of ideational function, this paper selects the commentary of city promotional films of Xi'an and San Francisco and analyzes them from the perspective of the transitivity system. The main purpose of this paper is to analyze the language skills of the two commentaries and to provide ideas and methods for the audience to understand such explanatory texts. This paper focuses on the following two questions: 1) How do the six processes of the transitivity system distribute in the two commentaries? 2) What are the specific functions of the six processes in the two commentaries? The results show that 1) there are two kinds of processes frequently used in explanatory texts, namely material process and relational process; 2) the frequency of mental, verbal and existential processes is relatively low; 3) behavioral process has no occurrence. The reason may be that although the textual structure and description focus of the two commentaries are different, they both belong to the applied style of oral explanation, so that they share the same social functions of shaping the city image, highlighting the city connotation and managing the city brand.